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A spokesman for Thomann-Hanry said: "A significant drawback of traditional cleaning methods is that they require buildings to be shrouded in scaffolding for months on end, inconveniencing occupants, staff and visitors alike and, in the case of university buildings, disrupting student life.

"And as these techniques use chemicals, detergents and water, contaminants can migrate further into the stonework, exacerbating the problem."

The company have also cleaned and restored King's College's Grade I-listed Gibbs’ Building.

The second-oldest building in the college, it dates back to the 1720s and was named after its architect William Gibbs, who also designed St Martin-in-the-Fields in London and Oxford’s Radcliffe Camera.

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"However, its primary advantage is the gentleness of the technique, making it ideal for heritage and listed buildings and, as a result, finding favour with historic England.

"Using this technique on King's College was ideal."

A spokesperson from King's College said: “By cleaning masonry without reliance on chemicals, water or detergent, Façade Gommage is a preferred choice for the presentation of historical buildings, as well as being much faster, cheaper and less disruptive.”